/*
 * Copyright 2002-2019 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.web.reactive.function.client;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.LinkedHashMap;
import java.util.List;
import java.util.Map;
import java.util.function.Consumer;

import org.springframework.http.HttpHeaders;
import org.springframework.http.client.reactive.ClientHttpConnector;
import org.springframework.http.client.reactive.JettyClientHttpConnector;
import org.springframework.http.client.reactive.ReactorClientHttpConnector;
import org.springframework.http.codec.ClientCodecConfigurer;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
import org.springframework.util.ClassUtils;
import org.springframework.util.CollectionUtils;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.util.DefaultUriBuilderFactory;
import org.springframework.web.util.UriBuilderFactory;

/**
 * Default implementation of {@link WebClient.Builder}.
 *
 * @author Rossen Stoyanchev
 * @author Brian Clozel
 * @since 5.0
 */
final class DefaultWebClientBuilder implements WebClient.Builder {

    private static final boolean reactorClientPresent;

    private static final boolean jettyClientPresent;

    static {
        ClassLoader loader = DefaultWebClientBuilder.class.getClassLoader();
        reactorClientPresent = ClassUtils.isPresent("reactor.netty.http.client.HttpClient", loader);
        jettyClientPresent = ClassUtils.isPresent("org.eclipse.jetty.client.HttpClient", loader);
    }


    @Nullable
    private String baseUrl;

    @Nullable
    private Map<String, ?> defaultUriVariables;

    @Nullable
    private UriBuilderFactory uriBuilderFactory;

    @Nullable
    private HttpHeaders defaultHeaders;

    @Nullable
    private MultiValueMap<String, String> defaultCookies;

    @Nullable
    private Consumer<WebClient.RequestHeadersSpec<?>> defaultRequest;

    @Nullable
    private List<ExchangeFilterFunction> filters;

    @Nullable
    private ClientHttpConnector connector;

    @Nullable
    private ExchangeStrategies strategies;

    @Nullable
    private List<Consumer<ExchangeStrategies.Builder>> strategiesConfigurers;

    @Nullable
    private ExchangeFunction exchangeFunction;


    public DefaultWebClientBuilder() {
    }

    public DefaultWebClientBuilder(DefaultWebClientBuilder other) {
        Assert.notNull(other, "DefaultWebClientBuilder must not be null");

        this.baseUrl = other.baseUrl;
        this.defaultUriVariables = (other.defaultUriVariables != null ?
                new LinkedHashMap<>(other.defaultUriVariables) : null);
        this.uriBuilderFactory = other.uriBuilderFactory;
        if (other.defaultHeaders != null) {
            this.defaultHeaders = new HttpHeaders();
            this.defaultHeaders.putAll(other.defaultHeaders);
        }
        else {
            this.defaultHeaders = null;
        }
        this.defaultCookies = (other.defaultCookies != null ?
                new LinkedMultiValueMap<>(other.defaultCookies) : null);
        this.defaultRequest = other.defaultRequest;
        this.filters = other.filters != null ? new ArrayList<>(other.filters) : null;
        this.connector = other.connector;
        this.strategies = other.strategies;
        this.exchangeFunction = other.exchangeFunction;
    }

    private static HttpHeaders unmodifiableCopy(HttpHeaders headers) {
        return HttpHeaders.readOnlyHttpHeaders(headers);
    }

    private static <K, V> MultiValueMap<K, V> unmodifiableCopy(MultiValueMap<K, V> map) {
        return CollectionUtils.unmodifiableMultiValueMap(new LinkedMultiValueMap<>(map));
    }

    @Override
    public WebClient.Builder baseUrl(String baseUrl) {
        this.baseUrl = baseUrl;
        return this;
    }

    @Override
    public WebClient.Builder defaultUriVariables(Map<String, ?> defaultUriVariables) {
        this.defaultUriVariables = defaultUriVariables;
        return this;
    }

    @Override
    public WebClient.Builder uriBuilderFactory(UriBuilderFactory uriBuilderFactory) {
        this.uriBuilderFactory = uriBuilderFactory;
        return this;
    }

    @Override
    public WebClient.Builder defaultHeader(String header, String... values) {
        initHeaders().put(header, Arrays.asList(values));
        return this;
    }

    @Override
    public WebClient.Builder defaultHeaders(Consumer<HttpHeaders> headersConsumer) {
        headersConsumer.accept(initHeaders());
        return this;
    }

    private HttpHeaders initHeaders() {
        if (this.defaultHeaders == null) {
            this.defaultHeaders = new HttpHeaders();
        }
        return this.defaultHeaders;
    }

    @Override
    public WebClient.Builder defaultCookie(String cookie, String... values) {
        initCookies().addAll(cookie, Arrays.asList(values));
        return this;
    }

    @Override
    public WebClient.Builder defaultCookies(Consumer<MultiValueMap<String, String>> cookiesConsumer) {
        cookiesConsumer.accept(initCookies());
        return this;
    }

    private MultiValueMap<String, String> initCookies() {
        if (this.defaultCookies == null) {
            this.defaultCookies = new LinkedMultiValueMap<>(4);
        }
        return this.defaultCookies;
    }

    @Override
    public WebClient.Builder defaultRequest(Consumer<WebClient.RequestHeadersSpec<?>> defaultRequest) {
        this.defaultRequest = this.defaultRequest != null ?
                this.defaultRequest.andThen(defaultRequest) : defaultRequest;
        return this;
    }

    @Override
    public WebClient.Builder filter(ExchangeFilterFunction filter) {
        Assert.notNull(filter, "ExchangeFilterFunction must not be null");
        initFilters().add(filter);
        return this;
    }

    @Override
    public WebClient.Builder filters(Consumer<List<ExchangeFilterFunction>> filtersConsumer) {
        filtersConsumer.accept(initFilters());
        return this;
    }

    private List<ExchangeFilterFunction> initFilters() {
        if (this.filters == null) {
            this.filters = new ArrayList<>();
        }
        return this.filters;
    }

    @Override
    public WebClient.Builder clientConnector(ClientHttpConnector connector) {
        this.connector = connector;
        return this;
    }

    @Override
    public WebClient.Builder codecs(Consumer<ClientCodecConfigurer> configurer) {
        if (this.strategiesConfigurers == null) {
            this.strategiesConfigurers = new ArrayList<>(4);
        }
        this.strategiesConfigurers.add(builder -> builder.codecs(configurer));
        return this;
    }

    @Override
    public WebClient.Builder exchangeStrategies(ExchangeStrategies strategies) {
        this.strategies = strategies;
        return this;
    }

    @SuppressWarnings("deprecation")
    @Override
    public WebClient.Builder exchangeStrategies(Consumer<ExchangeStrategies.Builder> configurer) {
        if (this.strategiesConfigurers == null) {
            this.strategiesConfigurers = new ArrayList<>(4);
        }
        this.strategiesConfigurers.add(configurer);
        return this;
    }

    @Override
    public WebClient.Builder exchangeFunction(ExchangeFunction exchangeFunction) {
        this.exchangeFunction = exchangeFunction;
        return this;
    }

    @Override
    public WebClient.Builder apply(Consumer<WebClient.Builder> builderConsumer) {
        builderConsumer.accept(this);
        return this;
    }

    @Override
    public WebClient.Builder clone() {
        return new DefaultWebClientBuilder(this);
    }

    @Override
    public WebClient build() {
        ExchangeFunction exchange = (this.exchangeFunction == null ?
                ExchangeFunctions.create(getOrInitConnector(), initExchangeStrategies()) :
                this.exchangeFunction);
        ExchangeFunction filteredExchange = (this.filters != null ? this.filters.stream()
                .reduce(ExchangeFilterFunction::andThen)
                .map(filter -> filter.apply(exchange))
                .orElse(exchange) : exchange);
        return new DefaultWebClient(filteredExchange, initUriBuilderFactory(),
                this.defaultHeaders != null ? unmodifiableCopy(this.defaultHeaders) : null,
                this.defaultCookies != null ? unmodifiableCopy(this.defaultCookies) : null,
                this.defaultRequest, new DefaultWebClientBuilder(this));
    }

    private ClientHttpConnector getOrInitConnector() {
        if (this.connector != null) {
            return this.connector;
        }
        else if (reactorClientPresent) {
            return new ReactorClientHttpConnector();
        }
        else if (jettyClientPresent) {
            return new JettyClientHttpConnector();
        }
        throw new IllegalStateException("No suitable default ClientHttpConnector found");
    }

    private ExchangeStrategies initExchangeStrategies() {
        if (CollectionUtils.isEmpty(this.strategiesConfigurers)) {
            return this.strategies != null ? this.strategies : ExchangeStrategies.withDefaults();
        }

        ExchangeStrategies.Builder builder =
                this.strategies != null ? this.strategies.mutate() : ExchangeStrategies.builder();

        this.strategiesConfigurers.forEach(configurer -> configurer.accept(builder));
        return builder.build();
    }

    private UriBuilderFactory initUriBuilderFactory() {
        if (this.uriBuilderFactory != null) {
            return this.uriBuilderFactory;
        }
        DefaultUriBuilderFactory factory = this.baseUrl != null ?
                new DefaultUriBuilderFactory(this.baseUrl) : new DefaultUriBuilderFactory();
        factory.setDefaultUriVariables(this.defaultUriVariables);
        return factory;
    }

}
